1. Field of the Invention
This invention relates to a means for solving the problem of negating the surrounding inward pressure and upward pressure of the earth material exerted towards the outside surface of a given vertical sanitary vent pipe which is to be buried and surrounded by the earth. Such vertical sanitary vent pipes, typically made from polyvinyl chloride (pvc), are or have been installed in thousands of home lots in northern parts of the United States; and within a time span, of such as short as one year or a few years after installation, upward pressure exerted upon such pipes by the repeated freezing and thawing of the ground near its surface causes the pipes to heave and become separated from the T-fitting traps to which they are originally connected, thereby leading to environmental and pollution problems, as are referred to in more detail hereinafter.
My pending application Ser. No. 689955, filed Apr. 23, 1991 describes an apparatus and method for helping to overcome such environmental and pollution problems by providing a novel means for re-inserting the vent pipes into their female T-fitting traps after they have been displaced therefrom by such freezing and thawing as described above. The present application is more particularly addressed to describing improved means for preventing such vent pipe displacement from occurring in the first place; and/or to improved means for re-inserting a new vent pipe into the T-fitting trap in such a way as to prevent the separation from re-occurring.
2. Description of the Related Art
A pre-examination search was carried out for any patents that might be anticipatory of applicant's invention and none were found. The search was conducted primarily in U.S. Classes 405/216; 405/217; and 405/231.
The following patents were noted in the search and the following brief comments relating to each explain why their teachings are different from the invention described in the instant patent application.
U.S. Pat. No. 4,464,083--The ice guard sleeve is not sectional as is the sleeve of the present invention. When the frost works on the sleeve of the patent, it works on the entire sleeve. When frost lifts a sleeve in the earth, the sleeve will not return to its original position because the earth friction at the lower part of the sleeve is greater as a holding factor than the ground is as a settling factor. This is not a factor in water, the sleeve environment in the patent, but it is an important factor as to the sleeve design and its purpose in the present invention.
U.S. Pat. No. 4,512,683--The piling is designed for water; not sectional vertically, (as is the sleeve of the present invention) but only horizontally, to be designed in two halves to be put around the pile. The sleeve is split for installation purposes, not for protectional function; if frost acted upon the sleeve of this patent in an earth environment, once lifted it would not re-settle for same reason as stated above re U.S. Pat. No. 4,464,083; also because of its corrugated nature, the frost might split it in half because the lower section would be anchored to the ground while the frost would act on the upper section causing a tensile stress on the entire unit.
U.S. Pat. No. 4,585,681--The pile of this patent requires a base mount to the pipe to secure the sleeve. The sleeve is not sectional, but a bellow stretching design and the frost forces liquid within its liner vertically above the ground to absorb the ground expansion. This base mount would have to be done prior to ground covering. This is in contrast to the sleeve of the present invention which has no physical anchoring to the pipe which it is protecting. This possible fatigue of the bellows caused by the expansion and contraction of the frost action in the long term could rupture the outer or inner membrane rendering the sleeve ineffective.
U.S. Pat. No. 4,818,148--The unit of this patent tries to reduce friction on the pile by coating the pile; which isn't effective enough to reduce the frost grip on an already smooth pvc vent pipe as is necessary to maintain vent pipe stability as used or required in the present application. The entire sleeve is acted upon; when frost moves the protector when it gets a grip on it, it moves the entire protector due to the fact it is not sectional.
The frost-proof sleeve of the present invention will work within a 1/2" larger radius duct tunnel than the tubular pipe that it originally surrounds; None of the sleeves in the above patents will do this. Also, in the invention of this application, the surface area of the original pipe is reduced from a 4" diameter pipe to 3" (25% reduction), which in turn reduces the gripping ability of the frost--this is not true of the designs in the above patents.
The design of none of the patents above (which were the references considered the closest art relevant to the present invention found in the search) uses a fixed frusto-conical design (an important aspect of each of the sleeve sections of the present invention) as its primary frost negating form. Because of its dominant frusto-conical nature, the frost effect actually wedges the sleeve downwards rather than lifting it up.